Calling actionListener using ajax4jsf is refreshing the whole page

Hi i have two datatables in one page and depending on the button i clicked one of the two should be disaplyed..I'm using ajax4jaf <a:jsFunction where i'm calling an actionListner on clicking the button and using the reRender attribute hiding/showing the datatables. But instead of only the tables refreshed whole page is getting refreshed..any clue on this?>